by Michael Winter, USA TODAY

Kerry Trotter, 20, of South Los Angeles was taken into custody by Los Angeles County sheriff's deputies, the Associated Press reports. Investigators said they received an anonymous tip after circulating a photo of the suspect taken from video of the 10-minute assault in the back of the Metropolitan Transit Agency bus in Culver City.

The only other person on the La Cienega Expo Line bus at 5 p.m. PT "attempted to get the bus driver's attention," the sheriff's department said, without explaining why he had failed.

The victim, an 18-year-old woman described as having the mental capacity of a 10-year-old, said that she and the suspect boarded the bus at the same stop and that he followed her to the back. The suspect left the bus at its last stop, and the victim reported the rape to the driver, the sheriff's department said.

The driver is being questioned.

The public buses are equipped with a silent alarm, and drivers are supposed to alert dispatchers if they suspect a crime.

An MTA spokesman called the rape "an extremely rare occurrence." Two other rapes aboard buses have been reported this year, AP says.